1. Field of the Invention
The present invention relates to an ophthalmic apparatus for observing an eye to be examined.
2. Description of Related Art
As ophthalmic apparatus for observing an eye to be examined, there have been known ophthalmic apparatus and others for observing interference fringes formed by a lacrimal layer on a cornea of the examinee""s eye, for example, to diagnose dry eye or the like.
However, such the prior art apparatus have a problem that flare would occur in an observation image, i.e., an image of the eye to be examined, and various problems caused by structures for preventing the occurrence of flare, or removing the flare. For instance, there is an apparatus in which polarizing plates are arranged in an illumination optical system and an observation optical system, respectively, of which optical paths are aligned coaxially to each other by a half-mirror, thereby preventing the occurrence of flare. This apparatus however includes a problem that fine positional adjustment to the polarizing plates is needed so that the direction of each polarization axis of the plates becomes proper. In addition, a quantity of light received by an imaging device such as a CCD camera or the like for observing, or photographing an image of an eye to be examined, would be reduced by the use of the half-mirror.
The present invention has been made in view of the above circumstances and has an object to overcome the above problems and to provide an ophthalmic apparatus with a simple structure capable of preventing the occurrence of flare and efficiently illuminating an eye to be examined.
Additional objects and advantages of the invention will be set forth in part in the description which follows and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
To achieve the purpose of the invention, there is provided an ophthalmic apparatus for observing an eye to be examined, the apparatus including: an observation optical system including an objective lens, for observing the eye through the objective lens; an illumination optical system including an illumination light source, for illuminating the eye through the objective lens; a polarization beam splitter having a property of transmitting one of linear polarized light beams that mutually perpendicularly intersect, and reflecting another linear polarized light beam, the polarization beam splitter being disposed opposite to the eye to be examined with respect to the objective lens, whereby aligning optical paths of the illumination and observation optical systems in a mutually coaxial relation; and a xc2xc wave plate disposed between the objective lens and the eye to be examined.